Hi all,
I'm trying to write a typical chat server application with twisted. At this moment, all is working fine except for some strange behaviour with sendLine and connectionLost funcs. Let me explain the problem:
- I have a server on the internet. - I connect two PCs (2 clients) from the same LAN through a router to that server - All is working fine until I disconnect the LAN of one of those PC (The client is disconnected but the server doesn't know about it). Just to test a typical wireless disconnection without closing sockets, etc... - After disconnecting I try to send some messages through the remaining clients to all clients through this function:
def sendMessageToAllClients(self, mesg,reqClient): for client in self.clientProtocols: dataLength = str(len(mesg)) if (len(dataLength) < 8): dif = 8 - len(dataLength) dataLength = "0"*dif + dataLength print "Enviando a:",str(client) client.sendLine(dataLength+mesg) client.clearLineBuffer()
As you can see, I send a message to all clients, including the one disconnected because the server doesn't know at this moment that the client is "out". I'm able to send 6 or 7 messages to the remaining client but after that, the connection get lost. I would expect to have a connectionLost with the client offline but actually I got a connectionLost in both clients and I don't know why. The server disconnect both clients with "non clean fashion".
Any help or advice would be highly appreciated.
Regards,
David
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On 26 May, 10:46 pm, djimenez@unipost.es wrote:
Hi all,
I'm trying to write a typical chat server application with twisted. At this moment, all is working fine except for some strange behaviour with sendLine and connectionLost funcs. Let me explain the problem:
- I have a server on the internet.
- I connect two PCs (2 clients) from the same LAN through a router to
that server
- All is working fine until I disconnect the LAN of one of those PC
(The client is disconnected but the server doesn't know about it). Just to test a typical wireless disconnection without closing sockets, etc...
- After disconnecting I try to send some messages through the remaining
clients to all clients through this function:
def sendMessageToAllClients(self, mesg,reqClient): for client in self.clientProtocols: dataLength = str(len(mesg)) if (len(dataLength) < 8): dif = 8 - len(dataLength) dataLength = "0"*dif + dataLength print "Enviando a:",str(client) client.sendLine(dataLength+mesg) client.clearLineBuffer()
You shouldn't be calling `client.clearLineBuffer()` here.
As you can see, I send a message to all clients, including the one disconnected because the server doesn't know at this moment that the client is "out". I'm able to send 6 or 7 messages to the remaining client but after that, the connection get lost. I would expect to have a connectionLost with the client offline but actually I got a connectionLost in both clients and I don't know why. The server disconnect both clients with "non clean fashion".
Any help or advice would be highly appreciated.
This is how TCP works. If the remote host stops responding to packets, then there's a period of time where the connection still appears to be up anyway. After a TCP-level timer expires, the connection is considered lost.
Jean-Paul
Hi Jean Paul,
A lot of thanks for your quick answer. It's really appreciated. Regarding your answer, I understand that when the remote hosts stop responding, after a timer, the connection is considered lost. But the main problem is that the remaining client (the one that have not been disconnected) should continue working without problems and the fact is that the server closes connection to that client too in a "non clean fashion".
Regards and a lot of thanks for your help,
David
De: twisted-web-bounces@twistedmatrix.com [twisted-web-bounces@twistedmatrix.com] En nombre de exarkun@twistedmatrix.com [exarkun@twistedmatrix.com] Enviado el: jueves, 27 de mayo de 2010 3:38 Para: Twisted Web World Asunto: Re: [Twisted-web] sendLine and connectionLost question
On 26 May, 10:46 pm, djimenez@unipost.es wrote:
Hi all,
I'm trying to write a typical chat server application with twisted. At this moment, all is working fine except for some strange behaviour with sendLine and connectionLost funcs. Let me explain the problem:
- I have a server on the internet.
- I connect two PCs (2 clients) from the same LAN through a router to
that server
- All is working fine until I disconnect the LAN of one of those PC
(The client is disconnected but the server doesn't know about it). Just to test a typical wireless disconnection without closing sockets, etc...
- After disconnecting I try to send some messages through the remaining
clients to all clients through this function:
def sendMessageToAllClients(self, mesg,reqClient): for client in self.clientProtocols: dataLength = str(len(mesg)) if (len(dataLength) < 8): dif = 8 - len(dataLength) dataLength = "0"*dif + dataLength print "Enviando a:",str(client) client.sendLine(dataLength+mesg) client.clearLineBuffer()
You shouldn't be calling `client.clearLineBuffer()` here.
As you can see, I send a message to all clients, including the one disconnected because the server doesn't know at this moment that the client is "out". I'm able to send 6 or 7 messages to the remaining client but after that, the connection get lost. I would expect to have a connectionLost with the client offline but actually I got a connectionLost in both clients and I don't know why. The server disconnect both clients with "non clean fashion".
Any help or advice would be highly appreciated.
This is how TCP works. If the remote host stops responding to packets, then there's a period of time where the connection still appears to be up anyway. After a TCP-level timer expires, the connection is considered lost.
Jean-Paul
_______________________________________________ Twisted-web mailing list Twisted-web@twistedmatrix.com http://twistedmatrix.com/cgi-bin/mailman/listinfo/twisted-web ------------------------------------------------------------------------------------------------------------------------------------------------ Este mensaje es confidencial y ata�e exclusivamente a las personas a las que va dirigido. Cualquier opini�n en el contenida, es exclusivo de su autor y no representa necesariamente la opinion de UNIPOST, S.A. Si Ud. no es el destinatario del mensaje, considerese advertido que lo ha recibido por error y que cualquier difusi�n o copia estan terminantemente prohibidos. Si ha recibido por error, por favor comuniquelo a UNIPOST, S.A. al n�mero +34 93 223 25 52 o correo electr�nico a support@unipost.es.
This e-mail is confidential and intended solely for the use of the individual to whom it is addressed. Any opinions presented are solely those of the author and do not necessarily represent those of UNIPOST, S.A. If you are not the intended recipient, be advised that you have received this e-mail in error and that dissemination, forwarding or copying of this e-mail is strictly prohibited. If you have received this e-mail in error please notify it to UNIPOST, S.A. by telephone on number +34 93 223 25 52 or by e-mail to support@unipost.es. ------------------------------------------------------------------------------------------------------------------------------------------------
On 06:42 am, djimenez@unipost.es wrote:
Hi Jean Paul,
A lot of thanks for your quick answer. It's really appreciated. Regarding your answer, I understand that when the remote hosts stop responding, after a timer, the connection is considered lost. But the main problem is that the remaining client (the one that have not been disconnected) should continue working without problems and the fact is that the server closes connection to that client too in a "non clean fashion".
Regards and a lot of thanks for your help,
Can you share a minimal example - http://sscce.org/ - that demonstrates this behavior?
Jean-Paul
participants (2)
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DAVID JIMENEZ CARRASCO -
exarkun＠twistedmatrix.com